1. Field of the Invention
The present invention relates to a slide adjusting device for use in forging press.
2. Prior Arts
As is well known, generally in a forging press, the upper section of a connecting rod is placed on an eccentric part of a crankshaft from the outside, and the lower section is divided into two fork-like parts in which a wrist pin is received by the top ends of the two fork-like parts. Since the wrist pin is inserted in the slide to support the slide at two ends in a suspended manner, the eccentric motion of the crankshaft is transformed to a vertical motion of the slide through the connecting rod and wrist pin, whereby a work piece held between an upper mold attached to the lower part of the slide and a lower mold mounted on a bed, is pressed to be forged by the mold.
The shape and size of the products formed by one forging press are not always constant, and the weight and volume of the work pieces to be forged vary at all times. Accordingly, the optimum load for pressing a work piece is not constant but should be adjusted whenever required. In an automatic continuous forging system equipped with a transfer machine for transferring consecutively work pieces using a plurality of molds, appropriate adjustment of the total load applied vertically from above is required, depending upon whether every mold is charged with a work piece or only a part of the molds is charged therewith. If this adjustment is not appropriate, there may arise such disadvantages as breakdown of the molds, insufficient forging, etc. As for the method of such adjustment, it has been popularly performed by adjusting the die height position by moving the vertically position of the slide, and actually several attempts for adjusting the slide of forging presses have been heretofore proposed.
In Japanese Utility Model Registration Publication (examined) No. 32478/1984, a device for adjusting the slide position is disclosed as shown in FIG. 5, and in which an adjusting lever 3a having an eccentric center Q1 dislocated from the center Q2 of a wrist pin 6a is disposed for turning the wrist pin. An adjusting screw 7a and a nut 5a mate with each other and are fixed to the adjusting lever 3a.The vertical position of the slide may be freely adjusted by turning the adjusting screw 7a either forwardly or reversely. It is described in this publication that since one end of the adjusting screw is movably supported at a cylinder mounted on the slide, adjustment of the slide position may be carried out by the vertical motion of the slide without reducing cylinder pressure.
In Japanese Laid-Open Patent Publication (unexamined) No. 75500/1990, another slide adjusting device is disclosed as shown in FIGS. 6, 7(A) and 7(B). A bearing section 32b is provided which is located in the middle part of an eccentric shaft 31b. The adjusting lever 3b is of an adjusting lever 3b disposed eccentrically from the center of two wrist pins 6b which are engaged with front end of a connecting rod 1b from the outside. Two sliders 101 are connected with each other through a link pin 102 and are received engagedly in the bearing section 32b so that a rod 9b inserted through the middle part of the link pin 102 and fixed thereto is coupled respectively with large and small cylinders 106, 104 each fixed to a slide 2b. One end of the rod 9b is fixed to a piston 105 sliding in the small cylinder 104 and the other end is fixed to another piston 107 sliding in the large cylinder 106. Accordingly, when supplying actuation oil into the large and small cylinders under equal feed pressure, a difference is produced in the force applied to the rod due to the difference between the areas of the two cylinders, whereby the rod is moved to the left, i.e., a load is applied so as to move the slide 2b downward (FIG. 6), thus enabling an adjustment which increases the load applied to a working piece (material).
Generally in the forging press of the mentioned type, slide adjustment is difficult by reason of space and, therefore, the adjustment has been preformed in most cases by providing an inclination on the lower side of a bolstar, i.e., by means of a wedge. It may be said that this well known adjustment method was largely improved by the previously mentioned prior art disclosed in Publication Nos. 32478/1984 and 75500/1990 from the viewpoint of simple operation and control. On the other hand, several disadvantages to be overcome still remain in these forging presses. That is, as shown in FIG. 5, the nut 5a performs a circular arc motion and together with the adjusting lever 3a establishes the center Q2 of the wrist pin as a fulcrum. Since the axis of the adjusting screw is linear, in order to perform such a circular arc motion, it is essential to dispose at least one universal joint 108 in the middle part of the adjusting screw to absorb a displacement between the linear motion and circular arc motion by curvature. As a result, the upper limit of the slide adjustable quantity is defined depending upon the performance of the universal joint, and the value of the upper limit is not so high at present.
Then, in the prior art shown in FIG. 6, the inclining motion of the adjusting lever is not performed by any forced drive, being different from the former prior art (FIG. 5), but the sliders 101 engagedly received in the bearing section 32b slide vertically and the link pin 102 held between the two sliders turns as it is held, moving horizontially along the straight rod 9b disposed through the link pin 102 and fixed thereto. Thus the adjusting lever 3b moves with the required inclination. In other words, as compared with the former prior art, the adjustable quantity of the slide is easily increased and therefore this latter prior art can meet large variations in the forging conditions, such as the shape of the mold. However, a still further problem to be overcome exists in manufacturing an apparatus of the mentioned construction. More specifically, the sliders 101 engagedly received in the bearing section 32b are in tight contact with the inside 32b-1 in the bearing section at four sides 101-1 thereof. The sliders 101 slide by receiving the movement of the rod through this surface contact. Accordingly, if the surface contact is insufficient at any of the four sides, looseness or backlash may arise inhibiting accurate slide adjustment. Thus, accuracy or precision in finish of such surfaces is a fatally important element in this prior art. However, it is not easy to finish internal surfaces of such a box-shaped member as used in this prior art precisely so as to achieve the mentioned slidable tight contact on each of the plural flat faces. Somewhat troublesome and high techniques are required for machining and assembling. Moreover, since bending stress is applied without fail to the rod 9b in this construction, a strength sufficient to handle such bending is required and, as a result, every component or member is obliged to be large-sized, which is a further disadvantage of these designs.